Can you do Amazon SEO for kindle ebooks just as well as you can optimize the rankings for the listings of physical products? Why even care about kindle ebooks you may ask, there is much more money to be made with pshysical products. But there is a whole lot of disadvantages to them as well. Firstly, there is just way more overhead, since you have to find a good supplier, order samples first, and have the capital to order your first batch.
But that's by far not the biggest problem you face when selling private label products. In my opinion the biggest advantage of kindle publishing compared to FBA is, that you don't have to deal with all the rules and regulations. It is definitely a challenge to conform to all the Amazon guidelines as well as FTC regulations.
This differs from category to category obviously, so I would stay far away from anything that goes into the mouth or on the skin like food supplements or beauty products. But even with clothing, or simple gadgets you can get yourself into trouble if they don't conform, since all your competitors are licking their fingers to catch you making a mistake and suing your ass.
With publishing kindle books, you don't have any of these issues. Maybe some copywrite claims could be made against you if you plagiarize, but you wouldn't do that right?
Just write a book yourself on a topic you're passionate about, or hire a ghost writer to write a book for you that solves a specific problem. It doesn't even have to be long. Just 20 pages are more than enough, if the quality of the information is good and it actually helps solve a problem, like losing weight, or making money online.
Just as with the normal product listings, anything that positively affects your CTR or CVR will also boost your rankings in the Amazon search. So make sure you get reviews and promote your book to push your best seller rank. A good title and cover image are also essential to stand out from the competition.